1)
x^{2}=-9" alt="x^{2}+9=0
x^{2}=-9" align="absmiddle" class="latex-formula">
нет решений
2) 
x(x-3)=0
X1=0
" alt="x^{2}-3x=0
x(x-3)=0
X1=0
" align="absmiddle" class="latex-formula"> или 
X2=3" alt="x-3=0
X2=3" align="absmiddle" class="latex-formula">

6x^{2}=-24 | :6
x^{2}=-4 " alt="3)6x^{2}+24=0
6x^{2}=-24 | :6
x^{2}=-4 " align="absmiddle" class="latex-formula">
нет решений